One vertex per element, one color per generator, with an edge from x to x·s.
(9,10)(11,20)(12,21)(13,16)(14,18)(15,19)(17,23)(22,24)(26,30)(28,36)(31,33)(34,37) involution — undirected(1,2)(3,7)(4,6)(5,8)(9,11,15,13)(10,16,19,20)(12,22,23,18)(14,17,24,21)(25,26,29,30)(27,33,35,31)(28,32,36,38)(34,40,37,39)(1,3)(2,5)(4,8)(6,7)(25,26,29,30)(27,31,35,33)(28,32,36,38)(34,39,37,40)(2,6)(5,7)(9,12,15,23)(10,17,19,21)(11,18,13,22)(14,20,24,16)(25,26)(27,33)(28,32)(29,30)(31,35)(34,40)(36,38)(37,39)(1,2)(3,5)(4,6)(7,8)(9,13,15,11)(10,16,19,20)(12,18,23,22)(14,17,24,21)(25,27,29,35)(26,31,30,33)(28,37,36,34)(32,40,38,39)(1,3)(2,7)(4,8)(5,6)(9,14,15,24)(10,18,19,22)(11,17,13,21)(12,20,23,16)(25,28,29,36)(26,32,30,38)(27,34,35,37)(31,39,33,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.